1. Field of the Invention
The present invention relates to hearing aids. The invention further relates to methods of making hearing aids. The invention more specifically concerns an ear plug for a hearing aid, which ear plug is made of a resilient material and is provided with an extraction cord for pulling the ear plug out of an ear canal. The invention still further relates to a method for manufacturing an ear plug
One general class of hearing aids comprises the behind-the-ear type with a housing placed behind the ear and an ear mould or ear plug arranged in the ear canal of the hearing aid user. The sound signal is picked up, amplified and processed in the behind-the-ear unit suitably to compensate the user's hearing deficiency, and transferred to the ear plug as an acoustic signal through a sound tube or as an electrical signal through a wire to a receiver or loudspeaker arranged in the ear mould.
For many hearing aid users a soft, pliable and resilient ear mould will be preferred as this will more easily adapt to the shape of the auditory canal wall, and thereby be more comfortable to the hearing aid user. Furthermore, a soft and resilient outer surface will make continuous adaptation to changes in the geometry of the ear canal feasible. Such changes in geometry may be caused e.g. when the hearing aid user is chewing or yawning.
2. The Prior Art
If the resilient ear plug is also custom fitted to the individual shape of the auditory canal this will be the optimum solution as this will minimize any localized mechanical pressure in the auditory canal. The custom fitted resilient ear plug may be manufactured according to the method described in PCT/EP2008/063663, published as WO-A1-2010040419.
In order to be able to remove such earplugs from the ear canal an extraction cord is often provided. An extraction cord projects out of the ear plug, and just outside, or close to the outside, of the ear canal, such that the person wearing the hearing aid can grab the extraction cord between two fingers and pull out the earplug from the ear canal.
WO-A1-98/51125 discloses an ear mould for a hearing aid, where the ear mould is made of a soft and pliable material such as silicone. The ear mould is provided with fins for obtaining a comfortable fit to the ear canal and for holding the ear mould in the ear by both friction and by mechanical locking. The ear mould is further provided with an extraction cord for pulling out the ear mould.